Trademark and Logos

A trademark is a word, phrase, symbol, and/or design that identifies and distinguishes the source of the goods of one party from those of others. A Service Mark is a word, phrase, symbol, and/or design that identifies and distinguishes the source of a service rather than goods. Some examples include: brand names, slogans, and logos. The term "trademark" is often used in a general sense to refer to both trademarks and service marks.

Unlike patents and copyrights, trademarks do not expire after a set term of years.  Trademark rights come from actual “use” (see below). Therefore, a trademark can last forever - so long as you continue to use the mark in commerce to indicate the source of goods and services.  A trademark registration can also last forever - so long as you file specific documents and pay fees at regular intervals.

SOURCE:- USPTO